Stabilization of styrene-acrylonitrile polymers with organic phosphites and vic-epoxy compounds



United; States Patent Office 7 i 3,189,570 STABILIZATION OFSTYRENE-ACRYLONITRILE POLYMERS WITH ORGANIC PHOSPHITES AND VIC-EPOXYCOMPOUNDS James S. Pavlin, Fitchburg, and Arnold B. Finestone,Leominster, Mass., assignors to Foster Grant 60., Inc., Leominster,Mass., a corporation of Delaware No Drawing. Filed Oct. 7, 1960, Ser.No. 61,095

12 Claims. (Cl. 260-23) This invention relates generally to new andimproved stabilized polymeric compositions, consisting essentially ofcopolymers of vinyl aryl compounds and acrylonitrile. More particularlythis invention relates to new and improved therrhoplastic polymericcompositions consisting of from about 65% to about 80% by weight ofvinyl aryl compounds and from about 35% to 20% by weight ofacrylonitrile having incorporated therein a combination of two classesof additives, i.e., an epoxidized organic. composition and an organicphosphite. I

' The polymeric compositions of this invention are known assolvent-resistant resins, viz., resins that are relatively resistant toattack by such liquids as gasoline, alcohol, water, aqueous acids andaqueous bases, even though they are swellable and/or dispersible in suchliquids as methyl ethyl ketone. As molding compositions, they arereadily moldable to clear and substantially nondiscolored products byconventional means such as by compression or injection molding, hotpressing, extrusion or the like. 1

Thermoplastic resinous compositions of from about 65% to 80% by weightof vinyl aryl compounds and from about 35 to 20% by weight ofacrylonitrile are known. These copolymers, which form the basis of thepresent invention, have average molecular weights such that by weightsolutions of the copolymers in methyl ethyl ketone have viscositiesbetween 6 and 40, preferably between 10- and 30, centipoises at atemperature of 25 C. The copolymers usually possess the most desirablecombination of mechanical properties, viz., strength, hardness,flexibility, and molding behavior, viz., flow rate, which combination ofmechanical properties and molding behavior is related to. the averagemolecular weight of the copolymers.

Several methods of preparing such thermoplastic resinous compositionsare knownto the art. For example,

bulk, solution, suspension and emulsion polymerization techniques havebeen employed.

Both thermal bulk polymerization and thermal solution polymerization ofstyrene and acrylonitrile may be carried out at temperatures rangingfrom about 60 C.

to about 180 C. under pressure. When thermal solution polymerizationtechniques are employed, hydrocarbon diluents such as benzene,ethylbenzene or the like are used, and such a polymerization processusually requires elaborate equipment to control the reaction and toremove unreacted monomers and/or diluents. In such a polymerization ithas been found advantageous to avoid the use of organic catalystsbecause of their eifect on the acceleration of the reaction rate thusincreasing the potential for an uncontrollably strong exothermic orrunaway polymer reaction.

Also known in the art is the polymerization of styrene and acrylonitrilein the presence of an emulsifying agent. Products thereby produced havenot received commercial acceptance because of the great difliculty inobtaining a clear and non-discolored product. In emulsion-polymerizationsystems, it is necessary to-take precautions to control the ultimatemolecular weight of the final product,

and because of the high water solubility of acrylonitrile, it isextremely difficult to obtain a uniform product. In

general, a higher percentage of acrylonitrile than that required in thecopolymerization is usually charged to a reactor in order to compensatefor the solubility of the monomer in water. Ordinarily, emulsion systemsare catalyzed by water soluble peroxy compounds, in amounts from 0.001to 1.0% of the polymerizable monomer. Examples are, hydrogen peroxide,sodium peroxide, the sodium salts of other .peroxy acids, the potassium,ammonium and other water soluble salts of the above or other peroxyacids and any other water soluble compounds containing a peroxy group(O-O--) which can generate radicals. reagents in the reaction mass canbe accomplished by agitation or by the use of wetting agents or emulsionstabilizers.

Commonly used wetting agents or emulsion stabilizers include the watersoluble or dispersible salts of fatty acids, such as sodium oleate andpotassium stearate, mixtures of water soluble fatty acid salts, such asthe common soaps prepared by the saponification of animal and vege-,table oils, the amino soaps such as triethanol amine and dodecyl methylamine, sulfonated hydrocarbons such' as alkyl aryl sulfonate and others.The quantity of em-ulsifying agent usually will depend upon theparticular L agent selected, the ratio of water and monomer to be used,

and other conditions of polymerization. In general, how'- ever, from 0.5to 5% by weight of the monomer may be employed.

It is also known in the art that the polymerization of styrene andacrylonitrile can be carried out in aqueous suspension, i.e'., in thepresence of a suspending agent, and that the products thereby made alsohave not received commercial acceptance becauseof the great difficultyin producing non-discolored uniform products. With respect to suspensionpolymerization, a relatively clear product can be obtained because ofthe ease with which the suspending agent is removed, but the product isunfavorably limited by the color produced. Again, as with the emulsionsystem, a greater concentration of acrylonitrile must be charged to areactor in order to compensate for the solubility of the acrylonitrilein water. 7

Normally, suspension polymerizationis accomplished at temperaturesvarying between 70 C. and 130 C. and preferably between 75 C. and 120 C.in the presence of 'a catalyst and a dispersing or suspending agent. Itis well known that peroxides such as benzoyl peroxide, acetyl peroxide,tertiary butyl hydroperoxide and diazo compounds such asazo-bis-isobutyrylnitrile can be used as catalysts in the polymerizationof styrene type com pounds with acrylonitrile. Commonly used suspendingagents include calcium hydroxyapatite, tricalcium phos phate, talc,polyacrylamide, methyl cellulose, methyl starch, glycol cellulose,polyvinyl alcohol, styrene-maleic acid copolymers, etc.

It is dilficult to prepare consistently good polymeric products in theforegoing proportions which are readily moldable to clear andnon-discolored products and which the copolymer is undesirably slow andthe molecular weight of the copolymer is undesirably high. On the otherhand, polymerization at temperatures calculated, to give desirableaverage molecular weight results in a reaction rate so great as to makeits control difiicult.

4 1 3,189,570 .Paten'te'd June 15, 19.65

The uniform distribution of the overheating.

The foregoing suspension system difficulties have been solved to someextent by polymerizing styrene and acrylonitrile, in the above mentionedproportions, in aqueous suspension at relatively low temperatures, viz.,60 to 125 C., and more preferably between 65 C. and 90 C., utilizing incombination a water insoluble aliphatic peroxide catalyst having thegeneral formula wherein n is an integer greater than two, preferably aninteger from 6 to 16, such a catalyst being exemplified by caprylyl,octanoyl, lauroyl, myristyl and stearyl peroxide and a third comonomerof the monovinyl aromatic type, i.e., alpha-methylstyrene. The styreneacrylonitrile polymers thus prepared in the presence of theaforementioned insoluble aliphatic peroxide catalyst and the monovinylcompound such as alpha-methylstyrene have relatively high uniformity,relatively good color, and relatively good color stability and do notappreciably discolor and are readily moldable to substantially clear andnon-discolored shaped products by conventional means, as more fullydisclosed and claimed in our co-pending U.S. application Serial No.21,146, filed April 11, 1960.

More specifically, as disclosed in our co-pending application, desirablepolymeric compositions consisting essentially of from about 65% to 80%by weight of styrene and alpha-methylstyrene and from about 35% to aboutby weight of acrylonitrile can be produced by suspension polymerizationinthe presence of a catalyst of the aforementioned type, the comonomeralpha-methylstyrene being present in the proportion of from about '5 toof the total amount of the monomers. lhe percentage ofalphamethylstyrene may be somewhat reduced in some cases, byincorporation in the system of a chain transfer agent, i.e., mercaptan,aliphatic halogenated compounds, aromatic hydrocarbons, unsaturateddimers of monomeric alpha-alkyl aromatic compounds, i.e., the dimer ofalphamethylstyrene, etc.

Preparation of the polymer by suspension polymerization in accordancewith our aforementioned.application is carried out by copolymerizing amonomer charge consisting of 20 to 35 parts of acrylonitrile, 2 to 10parts acrylonitrile in excess, and from 80 to 65 parts of styrene andalpha-m'ethylstyrene in an aqueous suspension at temperatures betweenpreferably about 65 C. and about 90 C. in the presence of a waterinsoluble aliphatic peroxide catalyst as described above. The catalystis present in the aqueous suspension in amounts of from about 0.02% to2.0%, and preferably between 0.1 to 1.6% by weight of the combinedweight of the monomers charged. Most efficient polymerization isachieved by controlling polymerization so that it may be stopped at aconversion in the range of from 60 to 92% preferably between 65 to 85%.

When thermal bulk polymerization techniques are employed, conversion isstopped within a range of about to 90% While in conventional emulsionpolymerization systems about 60 to 92% conversion is affected. In allmethods of polymerization, if polymerization is carried beyond thedesirable limit, a non-uniform copolymer will acrylonitrile in thecopolymer has a tendency to crosslinlc and gel with attendantdisadvantages to the product.

While the method of preparing polymeric compositions consistingessentially of vinyl aryl or styrene compounds and acrylonitrileby'theabove specificv suspension polym erization procedure has succeeded inproducing copolymer products which are clear and readily moldable tosubstantially clear and non-discolored products, we havefound that theseproducts can be substantially improved in these respects by theincorporation therein of the aforementioned two classes of organicadditives. v

More specifically we have now found that the incorporation of each oftwo additives, i.e., an epoxidized composition and an organic phosphitein polymeric compositions consisting of from about 65% to about byweight of vinyl aryl compounds and from about 35% to 20% by weight ofacrylonitrile, and having the previously recited average molecularweights, improve the stability of the polymeric compositions mostunexpectedly regardless of process, i.e., bulk, solution, emulsion "orsuspension, employed. Molding of these polymeric compositions atrelatively high temperatures does not result in loss of clarity but,unexpectedly in production of substantially non-discolored products.

The organic phosphites which can be used to advantage in the process ofthis invention are essentially the diand tri-organic esters ofphosphorous acid prepared by the esterification of phosphorous acid,with aliphatic, aromatic, aryl substituted aliphatic, alkyl substitutedaromatic alcohols or a mixture of one or more of thesealcohols.

Illustrative examples include the diand tri-methyl, ethyl, propyl,isopropyl, isobutyl, butyl, octyl, lauryl, cyclopentyl, cyclohexyl,ethylcyclohexyl, phenyl, benzyl, chlorophenyl, nitroph'enyl and naphthylphosphites, monobutyl diphenyl phosphites, diethyl monophenyl phosphite,monocresyl diphenyl phosphite, phenyl ethyl phosphite, tri-phenylethylphosphite, tri-phenylbutyl phosphite, tri-phenylhexyl phosphite,tri-phenyloctyl phosphite, tri-phenylethylhexyl phosphite,tri-tolylethyl phosphite. If an alkyl aryl phosphite is'employed, itshould preferably be substituted with alkyl groups containing eight ormore carbon atoms. Generally these alkyl aryl compounds prescribe to thegeneral formula:

(Ram

wherein R R and R are each similar or dissimilar, normal or branchedalkyl groups containing at least eight carbon atoms, and n is an integerof 1 or 2. The alkyl groups may be ortho, para, or meta to the oxygengroup. In addition to the alkyl substituent, the aromatic rings mayadditionally be substituted with relatively inert substituents, such asthe halogens, e.g., the fiuoro and chloro radicals; the nitro groups,such as nitro, nitroso, etc; Examples containing additional substituentsinclude tri -(ooctylphenyl) phosphite, tri (p-nonylphenyl) phosphite,tri (p-decylphenyl)phosphite, tri (p-undecyclphenyl) phosphite, tri(p-dodecylphenyl )phosphite, tri (p-tridecylphenyl) phosphite, tri(p-tetradecylphenyl) phosphite, tri (p-pentadecylphenyl) phosphite, tri(p-hexadecylphenyl) phosphite, tri(p-heptadecylphenyl) phosphite, tri(p-octadecylphenyl) phosphite, tri '(p-eicosyphenyl) phosphite,p-octylphenyl di (p-nonylphenyl) phosphite, p-nonylphenyl di(p-octylphenyl) phosphite, p-dodecylphenyl di (p-octylphenyl)phosphite,- tris (di-octylphenyl) phos- Mixtures of any two or moreofthe above phosphites may beer-n phite, tris (di-nonylphenyl) phosphite,etc.

ployed.

Epoxidized organic compositions which can be used to advantage in ourinvention are of three types. .First, are resinous complex mixtures ofpolyglycidyl ethers which are the products of the reaction of anepihalohydrin such as epichloroyor epibromohydrin and polyfunctionalpheabout 4 down to] depending upon'the functionality of the polyhydroxycompound employed.

Polyhydric phenols which have been found particularly suitable inpreparing epoxy resin useful in this invention are the reaction productsof phenol and aliphatic ketones, including polynuclear phenols whereinthe phenol nuclei are joined by carbon bridges such as p,pdihydroxydiphenyl dimethyl methane, p,p dihydroxydiphenyl methane,tris(p-hydroxyphenyl) methane, and 2,2,5,5 tetra (parahydroxyphenyl)hexane, etc. Examples of additional polynuclear phenols are those inwhich the phenol nuclei are joined by other than carbon bridges such ashis (p-hydroxyphenyl) sulfone, etc.

Suitable polyhydric alcohols used in preparing the present epoxy resinsinclude glycerol, propylene glycol, 1,4 butanediol, pentaerythritol,etc.

The second type epoxidized compositions suitable for use in ourinvention are those epoxy oils resulting from the epoxidation of suchwell known natural products as unsaturated oils which are glyceridesresulting from the esterification of trihydric alcohol glycerol withhigher and middle fatty acids, i.e., plant oils, olive oil, rape oil,

. almond oil, peanut oil, palm oil and soybean oil, etc. Oils oftheterpene series such as bomylene, camphene, carene, dipentene,fenchene, limonene, pinene, terpinene, etc., may also be epoxidized andare suitable for use in this invention. Well known epoxidizing agentssuch as peracetic acid may be employed to form these epoxidizedcompositions. The natural products are preferably substantiallyepoxidized so as to yield the highest oxirane concentration possible ineach molecule.

The third type of epoxidized compositions which we have found to besuitable for use in the present invention are the low molecular weightmaterials obtained from the epoxidation of cycloaliphatic compounds.Examples of useful products include dicyclopentadiene dioxide,di(isodecyl)4,5-epoxycyclohexane-l,Z-dicarboxylate, 3,4-epoxy- 6, methylcyclohexylmethyl 3,4 epoxy-fi-methylcyclohexanecarboxylate, di(2ethylhexyl)4,5 epoxycyclohexane-1,Z-dicarboxylate, etc. The oxiraneoxygen content of these materials preferably is high and is obtained bysubstantially complete epoxidation of the double bonded carbons in themolecules. It is desirable when using the second and third types ofepoxidized compositions that the oxirane content be as high as possibleand since low molecular weight liquid epoxy compounds are high inoxirane oxygen content they are preferred.

While the additives employed in this invention are most advantageouslyincorporated in the polymerizable comonomer prior to the polymerizationthereof, they may also be added during or after the polymerization.

In general, the epoxidized composition is usually used in amountsranging from about 0.005 to 0.75% by weight of the initial monomersemployed with from about 0.01 to 0.5% by Weight being preferred. The.concentration of the expoxidized composition varies within the broadrange specified depending on the particular oxirane content of themolecule in the specific epoxy employed. The phosphite may be employedin amounts ranging from about 0.005 to 0.75 by weight of the initialmonomers employed with from about 0.01 to 0.5% by weight beingpreferred.

The vinyl aryl, i.e., styrene type compounds which can be used inpreparing the copolymers of our invention are those compoundsrepresented by the following formula:

wherein R is selected from the group consisting of hydrogen and themethyl radical, R is a-substituent selected from the group consisting ofchlorine and lower alkyl radicals and n is an integer between and 2.Included are styrene per se, nuclear substituted alkyl styrenes, e.g.,o-, mand p-methyl styrene, 2-4 dimethylstyrene and the like, alpha andbeta alkyl substituted styrenes, e.g., alphamethylstyrene and the like.

' pounds may also be employed, i.e., a mixtureof styrene andalpha-methylstyrene as set forth above.

In place of acrylonitrile, methyl substituted acrylonitrile may beemployed to advantage in preparing the compositions of this invention.

A scale of color index numbers for visually comparing the polymericmaterials of this invention with each other and with polymers made bythe same methods but not incorporating the additives herein disclosedhas been devised. Molded examples for comparative purposes were preparedby pressing polymer beads into plaques at 370 F. and 450 F.,respectively, for 10 minutes. The scale in which the number is relatedto its adjacent color is as follows:

1. Water white 2. White 4. Very slightly yellow 6. Slightly yellow 8.Yellow 10. Very yellow 13. Dark yellow 20. Brown 20. Dark Brown Thefollowing examples illustrate the invention, but are not to be construedas limiting. In these examples parts are by weight, unless otherwisespecified.

Example 1 To a suitable pressure reaction vessel containing 200 parts ofdistilled water are added 50 parts of styrene monomer, 15 parts ofalpha-methylstyrene monomer, 35 parts of acrylonitrile, 1.4 part oflauroyl peroxide. The monomer mixture is polymerized at a temperature of80 C. in an inert atmosphere under autogenous pressure. Calcium.hydroxyapatite precipitated by a reaction between the required amountsof trisodium phosphate and calcium chloride is used as suspending agent.The degree of conversion is controlled by removal of the unreactedmonomer through steam distillation. Upon completion of thepolymerization, the polymer beads are thoroughly washed with water anddried in an air drier at C. to C. .In the final copolymer there is 25.5%'of com bined acrylonitrile, by weight of the copolymer. The polymer soformed has a viscosity of 16.2 centipoises when measured as a 10% byweight solution in methyl ethyl ketone at 25 C.

A portion of the polymer beads is pressed into a plaque at 370 F. andheld at that temperature for 10 minutes. The color index number is 7.Another portion of the beads is pressed into a plaque at 450 F. and heldat the temperature for 10 minutes. The color index number of the moldedplaque is 14.

for the lauroyl peroxide.

Employing the test molding conditions of Example 1 on the resultantproduct, the color index number of the test plaques molded at 370 F. and450 F. is greater than 20.

Example 3 Example 1 is repeated with the addition before polymerizationof'0.l part of Epon 828, a Shell Company polymer of epichlorohydrin andbisphenol A hav-' ing an average molecular weight of 390 grams and anepoxy equivalency of 054/100 grams, and 0.1 part of a mixture of 5 partstri-phenyl phosphite and parts of Mixtures of styrene comhis(nonylphenyl) phosphite. Employing the molding conditions of Example 1on the resultant product, the color index number of the test plaquemolded at 370 F. is 1 and the color index number of the test plaquemolded at 450 F. is 3.

Example 4 Example 1 is repeated with the addition before polymerizationof 0.1 part of 3,4-epoxy-6, methyl-cyclohexylmethyl3,4-epoxy-S-rnethyl-cyclohexanecarboxylate and 0.5 part of a mixture of5 parts of tri-phenyl phosphite and 95 parts of tris (nonylphenyl)phosphite. Employing the molding conditions of Example 1 on theresultant product the color index number of the test plaque molded at370 F. is 1 and the test plaque molded at 450 F. has a color indexnumber of 2.

Example 5 Example 2 is repeated with the addition before polymerizationof 0.5 part tris (nonylphenyl) phosphite and 0.5 part of Flexol E.P.O.,a Union Carbide Corp. substantially epoxidated soybean oil having anaverage viscosity of 536 centipoises at C. Employing the moldingconditions of Example 1 on the resultant product, the color indexnumber'of the test plaque molded at 370 F. is 5 and the color indexnumber of the test plaque molded at 450 F. is 10.

Example 6 Example 1 is repeated with the addition before polymerizationof 0.01 part of the Epon 828 of Example 3 and 0.01 part of a mixture of5 parts of tri-phenyl phosphite and 95 parts of tris (nonylphenyl)phosphite. Employing the molding conditions of Example 1 on theresultant product, the color index number of test plaque molded at 370F. is 3 and the color index number of the test plaque at 450 F. is 4.

Example 7 color index number of the plaque molded at 370 F. is

15 and the color index number of the plaque molded at '450" F. isgreater than 20.

Example 8 Example 7 is repeated with the addition before polymerizationof 0.5 part of tris (nonylphenyl) phosphite and 0.5 part of theepoxidized soybean oil of Example 5. Employingthe molding conditions ofExample 1 on the resultant product, the color index number of the testplaque molded at 370? F. is 4 and the test plaque molded at 450 F. has acolor indexof 6.

Example 9 To a conventional prebodying pot or still is charged 71 partsof styrene monomer and 29 parts of acrylonitrile. The polymerization iscarried out in the presence of 0.1 part of a suitable chain transferagent at a temperature of 125 C. in an inert atmosphere for a period of4 to 6 hours until a conversion of 70% is achieved, the polymerizationis interrupted and the unreacted monomer is removed out and thepolymer'cooled. Employing the molding conditions of Example 1 on theresultant product, the color of the test plaque molded at 370 F.

is 5 and the test plaque'molded at 450 F. has a co'lor index of 11.

. 8 Example 10 Example 9 is repeated with the addition beforepolymerization of 0.3 part of tris (nonylphenyl) phosphite and 0.1 partof substantially epoxidized dicyclopentadiene. Employing the moldingconditions of Example 1 on the resultant product, the color index numberof the plaque v molded at 370 F. is 1 and the color index number of theplaque molded at 450 F. is 2.

When styrene alone or other vinyl aryl compounds or mixtures thereof inamounts of to 80% by weight to 35 to 20% by weight of acrylonitrile areemployed in the above examples, similar advantageous results areobtained.

From the foregoing, it will be obvious that the use of mer products,said copolymer composition provided-by polymerization of a monomermixture of from about 65 to about 80% by weight of a polymerizablemonovinyl aryl compound and about 35 to about 20% by weight ofacrylonitrile in the presence of and in contact with (A) about 0.005 toabout 0.75% by weight, based on the monomer mixture, of an epoxystabilizing agent selected from the class consisting of (a) resinousreaction products of from 1 to 4 moles of an epihalohydrin and a mole ofa member selected from the group consisting of poly-. hydric phenols andpolyhydric aliphatic alcohols; (b) oils resulting from the epoxidationof a member selected from the group consisting of (1) a glyceridereaction product of a fatty acid and glycerol and (2) a terpene oil; and(c) low molecular weight epoxy cycloaliphatic compounds other thanepoxidizedterpene oils, said cycloaliphatic compounds being free ofvie-epoxy reactive substituents which interfere withthe desiredstabilization, and (B) about 0.005 to about 0.75% by weight, based onthe monomer mixture, of an organic phosphite selected from the classconsisting of aryl and alkylaryl diand trisu-bstituted phosphites.

2. A thermoplastic acrylonitrile-monovinyl aryl c0- polymer compositionwhich is conventionally moldable to clear and substantiallynon-discolored uniform copolymer products, said copolymer compositionprovided by polymerization of a monomer mixture of from about 30% toabout by weight of styrene, about 5% to about 35% of alphamethylstyreneand about 35 to about 20% by Weight of acrylonitrile in the presence ofand in contact with (A) about 0.005 to about 0.75 by weight, based onthe monomer mixture, of an epoxy stabilizing agent selected from thegroup consisting of (a) resinous reaction products of from 1 to 4 moles.of an epihalohydrin and a mole of a member selected from the groupconsisting of polyhydric phenols and polyhydric aliphatic alcohols; (b)oils resulting from the epoxidation of. a 1

member selected from the group consisting of (1) a glyceride reactionproduct of a fatty acid and glycerol and (2) a terpene oil; and (c) lowmolecular weight epoxy cycloaliphatic compounds other than epoxidizedterpene oils, said' cycloaliphatic compounds being free of vicepoxyreactive substituents which interfere with the desired stabilization,and (B). about 0.005 to about 0.75% by weight, based on the monomermixture, of an organic phosphite selected from the class consistingolfaryl and alkylaryl diandrtri-substituted phosphites.

9 3. A thermoplastic polymeric composition of claim 1 wherein the epoxystabilizing agent and the organic phosphite are employed in amounts ofabout 0.01 to about 0.5%, respectively.

4. A thermoplastic polymeric composition of claim 1' wherein thestabilizing agent employed is an epoxidation oil as defined therein.

5. A thermoplastic polymeric composition of claim 1 v wherein thestabilizing agent employed is a resinous epithe desired stabilization.

7. A thermoplastic polymeric composition of claim 1 wherein the organicphosphite employed is an alkylaryl phosphite asdefined therein.

8. A thermoplastic polymeric composition of claim 1 wherein the organicphosphite employed is an arylphosphite as defined therein.

9. A method of producing a thermoplastic acrylonitrilemonovinyl arylcopolymer composition which is capable of being conventionally molded toclear and substantially non-discolored uniform copolymer parts, saidmethod comprising polymerization of a monomer mixture of from about 65to about 80% by weight of a polymerizable monovinyl aryl compound andabout 35 to about 20% by weight of acrylonitrile in the presence of andin contact with (A) about 0.005 to about 0.75% by weight, based on themonomer mixture, of an epoxy stabilizing agent selected from the groupconsisting of (a) resinous reaction products of from 1 to 4 moles of anepihalohydrin and one mole of a member selected from the groupconsisting of polyhydric phenols and polyhydric aliphatic alcohols; (b)oils resulting from the epoxidation of a member selected from the groupconsisting of 1) a glyceride reaction product of a fatty acid andglycerol and (2) a terpene oil; and (c) low molecular weight epoxycycloaliphatic compound other than an epoxidized terpene oil, saidcycloaliphatic compound being free of vie-epoxy reactive substituentswhich interfere with the desired s'tabi-' lization, and (B) about 0.005to about 0.75% by weight, based on the monomer mixture, of an organicphosphite selected from the class consisting of aryl and alkylar yldiand tri-substituted phosphites.

10. A polymerization method of claim 9 wherein styrene is employed as amonovinyl aryl compound.

11. A method of claim 9 characterized by being an aqueous suspensionpolymerization.

12. A method of claim 9 wherein a monomer mixture of from about 30% toabout 75% by weight of styrene, about 5% to about 35% by weight ofalpha-methylstyrene and about 35 to about 20% by weight ofacrylonitrile, is employed.

References Cited by the Examiner UNITED STATES PATENTS 2,733,226 1/56Hunter 260-45.7 2,779,771 1/57 Phillips 260-453 2,811,505 10/57 Schulkenet a1 260-45.8 2,878,229 3/59 Jenkins et al 260-45.7 2,889,308 6/59Fedderson 260-23 XR 2,898,348 8/59 Swern et a1 26023 2,949,474 8/60Murdoch et al 260-45.8 2,951,055 8/60 Luttinger 26045.7 2,963,455 12/60Rowland et a1 260-458 A. D. SULLIVAN, Examiner.

1. A THERMOPLASTIC ACRYLONITRILE-MONOVINYL ARYL COPOLYMER COMPOSITIONWHICH IS CONVENTIONALLY MOLDABLE TO CLEAR AND SUBSTANTIALLYNON-DISCOLORED UNIFORM COPOLYMER PRODUCTS, SAID COPOLYMER COMPOSITIONPROVIDED BY POLYMERIZATION OF A MONOMER MIXTURE OF FROM ABOUT 65 TOABOUT 80% BY WEIGHT OF A POLYMERIZABLE MONOVINYL ARYL COMPOUND AND ABOUT35 TO ABOUT 20% BY WEIGHT OF ACRYLONITRILE IN THE PRESENCE OF AND INCONTACT WITH (A) ABOUT 0.005 TO ABOUT 0.75% BY WEIGHT, BASED ON THEMONOMER MIXTURE, OF ANY EPOXY STABILIZING AGENT SELECTED FROM THE CLASSCONSISTING OF (A) RESINOUS REACTION PRODUCTS OF FROM 1 TO 4 MOLES OF ANEPIHALOHYDRIN AND A MOLE OF A MEMBER SELECTED FROM THE GROUP CONSISTINGOF POLYHYDRIC PHENOLS AND POLYHYDRIC ALIPHATIC ALCOHOLS; (B) OILSRESULTING FROM THE EPOXIDATION OF A MEMBER SELECTED FROM THE GROUPCONSISTING OF (1) A GLYCERIDE REACTION PRODUCT OF A FATTY ACID ANDGLYCEROL AND (2) A TERPENE OIL; AND (C) LOW MOLECULAR WEIGHT EPOXYCYCLOALIPHATIC COMPOUNDS OTHER THAN EPOXIDIZED TERPENE OILS, SAIDCYCLOALIPHATIC COMPOUNDS BEING FREE OF VIC-EPOXY REACTIVE SUBSTITUENTSWHICH INTERFERE WITH THE DESIRED STABILIZATION, AND (B) ABOUT 0.005 TOABOUT 0.75% BY WEIGHT, BASED ON THE MONOMER MIXTURE, OF AN ORGANICPHOSPHITE SELECTED FROM THE CLASS CONSISTING OF ARYL AND ALKYLARYL DI-AND TRISUBSTITUTED PHOSPHITES.